Collection devices are a type of cap and vessel combination commonly used for receiving and storing biological specimens for delivery to clinical laboratories, where the specimens may be analyzed to determine the existence or state of a particular condition or the presence of a particular infectious agent. Types of biological specimens commonly collected and delivered to clinical laboratories for analysis include blood, urine, sputum, saliva, pus, mucous and cerebrospinal fluid. Since these specimen-types may contain pathogenic organisms, it is important to ensure that collection devices are constructed to be essentially leak-proof during transport from the site of collection to the site of analysis. This feature of collection devices is particularly critical in those cases where the clinical laboratory and the collection facility are remote from one another.
To prevent leakage, collection device caps are typically designed to be screwed, snapped or otherwise frictionally fitted onto the vessel component, thereby forming an essentially leak-proof seal between the cap and the vessel. In addition to preventing leakage of the specimen, an essentially leak-proof seal formed between the cap and the vessel of a collection device will also ameliorate exposure of the specimen to potentially contaminating influences from the surrounding environment. This aspect of a leak-proof seal is important for preventing the introduction of contaminants that could alter the qualitative or quantitative results of an assay.
While a leak-proof seal should prevent specimen seepage during transport, the physical removal of the cap from the vessel prior to specimen analysis presents another opportunity for contamination. When removing the cap, specimen which may have collected on the under-side of the cap during transport could come into contact with a practitioner, possibly exposing the practitioner to harmful pathogens present in the fluid sample. And if the specimen is proteinaceous or mucoid in nature, or if the transport medium contains detergents or surfactants, then a film or bubbles which may have formed around the mouth of the vessel during transport can burst when the cap is removed from the vessel, thereby disseminating specimen into the environment. It is also possible that specimen residue from one collection device, which may have transferred to the gloved hand of a practitioner, will come into contact with specimen from another collection device through routine or careless removal of the caps. Another risk is the potential for creating a contaminating aerosol when the cap and the vessel are physically separated from one another, possibly leading to false positives or exaggerated results in other specimens being simultaneously or subsequently assayed in the same general work area through cross-contamination.
Concerns with cross-contamination are especially acute when the assay being performed involves nucleic acid detection and includes an amplification procedure. There are many procedures in use for amplifying nucleic acids, including the polymerase chain reaction (PCR), (see, e.g., Mullis, “Process for Amplifying, Detecting, and/or Cloning Nucleic Acid Sequences,” U.S. Pat. No. 4,683,195), transcription-mediated amplification (TMA), (see, e.g., Kacian et al., “Nucleic Acid Sequence Amplification Methods,” U.S. Pat. No. 5,399,491), ligase chain reaction (LCR), (see, e.g., Birkenmeyer, “Amplification of Target Nucleic Acids Using Gap Filling Ligase Chain Reaction,” U.S. Pat. No. 5,427,930), strand displacement amplification (SDA), (see, e.g., Walker, “Strand Displacement Amplification,” U.S. Pat. No. 5,455,166), and loop-mediated isothermal amplification (see, e.g., Notomi et al., “Process for Synthesizing Nucleic Acid,” U.S. Pat. No. 6,410,278). A review of several amplification procedures currently in use, including PCR and TMA, is provided in HELEN H. LEE ET AL., NUCLEIC ACID AMPLIFICATION TECHNOLOGIES (1997).
Since amplification is intended to enhance assay sensitivity by increasing the quantity of targeted nucleic acid sequences present in a specimen, transferring even a minute amount of pathogen-bearing specimen from another container, or target nucleic acid from a positive control sample, to an otherwise negative specimen could result in a false-positive result. To minimize the potential for creating contaminating specimen aerosols, and to limit direct contact between specimens and humans or the environment, it is desirable to have a collection device cap which can be penetrated by a fluid transfer device (e.g., pipette tip) while the cap remains physically and sealably associated with the vessel. And, to prevent damage to the fluid transfer device which could effect its ability to predictably and reliably dispense or draw fluids, the cap design should limit the forces necessary for the fluid transfer device to penetrate the cap. Ideally, the collection device could be used in both manual and automated formats and would be suited for use with pipette tips made of a plastic material.
In addition, when a sealed collection device is penetrated, the volume of space occupied by a fluid transfer device will displace an equivalent volume of air from within the collection device. Therefore, it would be desirable to have a fluid transfer device with means for permitting air to be released from a collection device at a controlled rate as the fluid transfer device penetrates a surface of the collection device (e.g., associated cap). Without such means, a pressurized movement of air from the collection device into the surrounding environment could promote the formation and release of potentially harmful or contaminating aerosols, or bubbles in those instances where proteins or surfactants are present in the fluid sample. Therefore, a fluid transfer device which facilitates a controlled release of air from a penetrated collection device is needed to prevent or minimize the release of fluid sample in the form of aerosols or bubbles.